Giants Citizen Kabuto osx?

I have just installed Giants Citizen Kabuto on my i3 Imac (OSX 10.6.7)
and every time i open it, it fullscreens black as with most games but then shows a low res image of the desktop and immediatley quits. with 'Giants quit unexpectedly' message. Can anybody think of how to fix this? I really want to play giants again.

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